1 Field of the Invention
This invention relates to a discrimination method for analyzing and evaluating various chemical and physical quantities (hereinafter referred to as "chemical/physical quantities") including, for example, the species and nature of molecules whose chemical stimulation is sensed as odor or taste, the frequency band and quality of sound, and the wavelength band and color of light, and to an apparatus for conducting the method.
2 Description of the Prior Art
The conventional method of detecting and discriminating a chemical/physical quantity has consisted of setting up a plurality of sensors having differing sensitivities with respect to the respective components of the chemical/physical quantity, exposing the sensors to stimulation, waiting a prescribed period of time considered sufficient for the sensor outputs to reach and stabilize at higher than prescribed levels, and either deriving or comparing the sensor levels for evaluating the stimulation (chemical/physical quantity to which the sensors were exposed).
In a system for evaluating audible sound, for example, the incident stimulation (audible sound) has been analyzed and the sound quality evaluated by dividing the audible range (20-20,000 Hz) into n number of frequency bands (where n is a positive integer greater than 1) or into n number of successive frequency bands whose center frequencies differ by one octave in the manner of 20 Hz, 40 Hz, 80 Hz, 160 Hz, 320 Hz . . . , setting up n number of sensors each having the highest sensitivity in one of the respective bands or setting up n number of acoustic sensors tuned to high Q values at the respective center frequencies (so as to exhibit sharp bandpass filter characteristics), deriving stable transduced voltages (currents) from the sensors, and determining the sound pressures of the individual frequency components of the incident stimulation (audible sound). The measurement resolution and the evaluation accuracy increase with the number of divisions n.
Color and light have been evaluated in a similar manner. Specifically, the analysis and evaluation has been conducted by dividing the light wavelength range into nnumber of bands, using n number of photoelectric converters each having high sensitivity in one of the bands as sensors serving as bandpass filters with differing center frequencies, and using the light intensity information obtained after the sensor outputs have stabilized as the basis for determining the intensity of the respective frequency components of the incident stimulation (light or color).
Basically the same method has also been used for other physical and chemical quantities. Even odor and taste, traditionally considered to be peculiar to living organisms, have become the target of intensive research into ways for analyzing and discriminating stimulation by electrical and electronic means. Published reports regarding odorants include, for example, Nature, 1982, Vol. 299,352-355 (Ref. no. 1); Nikkei Science, October 1991, 68-76 (Ref. no. 2), and T.IEE Japan, 1993, Vol. C 113, 621-626 (Ref. no. 3). In each of these earlier reports, however, the sensor outputs are derived and evaluated after the output values of the sensors have become greater than a prescribed level.
As will be understood from the foregoing, the prior art method of evaluating chemical/physical quantities is time consuming because the constituents of the chemical/physical quantity can be derived and the chemical/physical quantity be evaluated only after the sensor outputs have stabilized. Depending on the type of stimulation to be evaluated, the time required for the sensor outputs to stabilize may be very long.
Another problem of the prior art method is that measurement frequently becomes impossible when the incident stimulation is intense because the sensor outputs saturate before the end of the measurement period.
This invention was accomplished in response to the foregoing circumstances and has as its object to provide a method and apparatus for discriminating a chemical/physical quantity that enable the chemical/physical quantity analysis and evaluation to be conducted at high speed without degradation of evaluation capability owing to sensor saturation.